It was closed. He was on one side and Rose was on the other – and that was that. He could feel a numbness intertwine itself amongst his usually exceptionally sharp senses. For what could have been a split second or a day – his perception of time had gone – he didn't move. Instead, he just stared blankly at the wall that, although white and bland, was the source of the jagged and pointed stabs of his heart thumping inside his chest. He could hardly bear to look at it anymore and yet, he couldn't look away. His eyes were wide; his breath had unconsciously stopped in his lungs. A microscopic illogical but wishful smidgeon of hope partly expected Rose to reappear again at any moment.

She'd gain her balance and take a quick look around.

Her eyes would quickly come to rest on him.

Just for a moment, she'd hold his gaze just to make sure it was him – and then she'd positively beam as he'd step forward and pull her into a hug.

Despite the fact he knew he was wishing for the impossible, he couldn't help but feel slightly disappointed when he remained the sole occupant of the room.

This...whatever this he was feeling was...it was different. He'd done the same thing to her twice: once before in a different form when he'd tricked her onto the Tardis and programmed it to take her back to her own time, and just now when he'd slipped the device around her neck from behind and pressed the button. Both times he'd known for sure – he'd thought he'd known for sure – that he would never see her again. This time he knew for sure that they would never meet again. And yet somehow, it was indeed different.

Perhaps it was because, before, it had been quick, in the heat of the moment: that moment when he'd pointed the Sonic Screwdriver at the Tardis, when he'd hit that yellow button...he'd done these things without a second's thought, with only one thing in mind.

He had had to get Rose home safe, to her Mum, just as he'd always promised.

It was like it didn't matter whether or not he'd see her again because she was safe – and that was enough.

But she was safe now, wasn't she? He'd seen Pete appear to pull her into the other dimension before the void swallowed her, so why was it so hard finding comfort in the knowledge she was okay?

Perhaps it was the fact she was willing to leave all the people she cared about to stay with him, facing incomprehensible dangers alongside he and his Tardis, ten times more often than Mickey would have changed the oil in his car.

Or perhaps it had been the stubborn loyalty she'd shown to him, her determination to see this thing through to the end with him instead of doing what he would have much preferred her to – to be safe and live the fantastic life he knew she was capable of on the other side. Maybe he'd realized in a moment just how much he did appreciate her company on his voyages through time and space – and in that same moment he'd made it that much harder to watch her slip through the crack between dimensions.

But, it was more likely it was the knowing, final look he'd seen on her face as she'd disappeared - the split second comprehension and panic that overtook her right after it was too late.

He waged war against the numbness in his mind; he was getting the upper hand. It was just enough to control his feet. Deliberate, controlled steps, one foot at a time, he approached where the tear had once been. Rubber on cement, his footfalls were like the bass beneath the frenzied rhythm of his heart, driving home each moment of emotion as it came to pass.

He could feel her. Through the rip between the dimensions that was no longer there, he could feel her. It was horrible. He could smell the huge portion of sadness, the similarly large presence of guilt, and more than a little bit of the niggling sensation of loneliness in the saline smell of her tears that he found himself being able to detect. He felt...sorry, so very sorry. It was his fault – it was him that sent her across the rift that extra time, he that had caused her to gain more of the particles that made it just that bit harder for her to hold on; he that hadn't been able to reach her; he that hadn't been able to come up with one of his brilliant, just-in-the-nick-of-time plans to pull her back. And worst of all, he couldn't apologize. He couldn't just give her a hug to make it better, not this time.

The Torchwood building had been thrown into complete silence, and it rung in his ears. Maybe, just maybe, she would hear him if he just...

He pressed his ear and hands to the wall, listening, hoping...maybe she'd feel him there, know what he wanted to say.

I'm sorry...I'm so sorry.

Here, he found himself lingering.

He thought he had become accustomed to moving on. He could live forever, or at least that's what it felt like. The things around him would evolve while he stayed the same. Every world he knew would eventually die, and so would its people, regardless of who they were to him. The people he travelled with, his companions, would move on, find something for themselves to live for and they'd leave him. That was the way it had always worked.

When his companions had died, it had been him that had been left behind to mourn them. When they had moved on from the life the TARDIS gave them, he had been left behind to continue his travels alone. When their memories had been wiped, only he was left behind with the times that they'd spent together, the things that they'd done.

And he could deal with these things – more than a lifetime of practice had seen to that.

But Rose... "Forever," she'd said to him, and he had no doubt in his mind that "forever" she'd meant. She'd not left him to go to the realm of death, nor had she found something worth living for off the TARDIS. She'd not had every moment she'd spent exploring the galaxy removed from her mind: the intrigue, the excitement, the danger...all the moments in which she'd realized just how wonderful and interesting the universe could be would still be there. Maybe in time she'd look at these memories with fond recollection, but for now, he knew she wouldn't – she couldn't. Everything she'd miss, everything she could never do again...that's what she'd see in them. And it would eat her up inside.

As for himself, over the past few years, despite his several forms, one thing had not changed at all. He'd jump from one adventure to another, with more than the occasional misadventure along the way. He'd see what he needed to see, do what needed to be done and with hardly a breath in between he was back on the Tardis to the next burst of excitement. So, here, the Cybermen and the Daleks were gone. Rose, Jackie, Mickey, Pete, Jake...everyone here he'd worked with were gone. So why was he still here? What had Rose Tyler done to him that made him want to cling to the single moment in time and never let go? Why wasn't it as characteristically easy for him to pick up and move on, just like he always had?

He may as well have been seeing her standing there, tears uncontrollably spilling from her eyes as she demanded the universe - Mickey, Jackie, anyone - to let her return, until she simply faded into a resigned silence. Now, he usually celebrated his revelations with a whoop and an excited explanation, but as he came to realise this one, he permitted it only to hover idly in between his two hearts. This feeling he felt was different, was something new; was awful.

He wasn't the one being left behind this time.

His logic inevitably came to take firm hold of him – he couldn't stay here forever. Forcing every muscle, he lowered his hands and removed his ear from against the wall. Something broke; he had to let go.

In a breath, he pulled himself together and, turning with his hands deep in his pockets, the Doctor walked away.